Anthropic reveals Claude Mythos Preview, withholds it over cyber risk and launches Project Glasswing
On April 7, 2026 Anthropic disclosed Claude Mythos Preview, a general-purpose frontier model so strong at finding and exploiting software vulnerabilities that Anthropic declined to release it generally. It found thousands of high-severity zero-days, including a 27-year-old OpenBSD bug. Anthropic instead gave access to Project Glasswing, a defensive coalition of AWS, Apple, Google, Microsoft, NVIDIA, CrowdStrike and others, backed by $100M in usage credits.
Key facts
- Announced April 7, 2026 after drafts leaked on March 26, 2026
- SWE-bench Verified 93.9% (Opus 4.6: 80.8%); SWE-bench Pro 77.8% (53.4%); Terminal-Bench 2.0 82.0% (65.4%); CyberGym 83.1% (66.6%)
- Found thousands of zero-days across major OSes and browsers: a 27-year-old OpenBSD remote-crash flaw, a 16-year-old FFmpeg bug, Linux kernel privilege escalations
- Glasswing launch partners: AWS, Anthropic, Apple, Broadcom, Cisco, CrowdStrike, Google, JPMorganChase, Linux Foundation, Microsoft, NVIDIA, Palo Alto Networks + 40 more
- $100M in Mythos Preview credits; $2.5M to Alpha-Omega/OpenSSF; $1.5M to Apache Software Foundation
- Participant pricing $25 / $125 per 1M tokens
- Mozilla later reported 271 Firefox vulnerabilities found with Mythos Preview (Apr 21); Glasswing grew from 50 to 200 organizations on June 2
What happened
Per Wikipedia's timeline, the announcement set off a wave of government reactions. US Treasury Secretary Bessent and Fed Chair Powell convened financial executives on April 9. The White House met Anthropic on April 16. India's Finance Ministry and Japan's FSA held meetings on April 23–24, and 32 US Representatives wrote to the National Cyber Director on May 13. Wikipedia also reports that unauthorized users got access on launch day via details from the Mercor data breach.
Why it matters
Mythos Preview marked the point where a frontier lab judged a model's offensive cyber capability too dangerous for general release. It shaped the rest of Anthropic's 2026: the Fable/Mythos safeguard split, verification programs and export-control fights.
Changelog
- 2026-09-29: added post link(s) (posts-as-events pass)
- 2026-09-29: created
Videos (17)
An initiative to secure the world's software | Project Glasswing
Anthropic · 2026-04-07 · officialAnthropic presents an official announcement introducing Claude Mythos Preview, a frontier AI model exhibiting advanced cybersecurity capabilities, alongside "Project Glasswing." The video features Anthropic leadership (CEO Dario Amodei, red team lead Logan Graham, researcher Nicholas Carlini) together with security…
This AI Short Drama Was Made With Claude Mythos + Higgsfield MCP ($10)
TOAST · 2026-06-16 · ai-madeThis short video, shared by creator TOAST, showcases an AI-generated fantasy action-comedy drama clip created using Anthropic's Claude Mythos paired with Higgsfield via the Model Context Protocol (MCP). The narrative follows an arena battle involving zodiac-summoning powers, an armored minotaur, a scorpion creature…
The Claude Mythos Story
Bitten Tech · 2026-06-01 · communityIn this video, presenter Saksham Choudhary from the YouTube channel Bitten Tech recounts the story surrounding the leak and capabilities of Anthropic's unreleased model, Claude Mythos Preview, and the subsequent formation of Project Glasswing. He analyzes the cybersecurity implications of agentic AI models with…
Claude Mythos: Why This Time Is Different
Absolutely Agentic · 2026-05-02 · communityIn this video from the channel Absolutely Agentic, the presenter discusses the events surrounding the leaked and subsequently gated release of Anthropic’s "Claude Mythos Preview" in late March and April 2026. He details Mythos’s dramatic benchmark leap in coding and automated cybersecurity exploitation, the launch of…
Claude Mythos: Highlights from 244-page Release
AI Explained · 2026-05-02 · communityPresented by the host of the YouTube channel AI Explained, this video breaks down the 244-page system card and supplementary alignment reports released for Anthropic’s frontier model, Claude Mythos Preview. The presenter examines why Anthropic decided against a general public release—restricting access to defensive…
Anthropic’s New Claude MYTHOS Is The Most Powerful AI Ever!
AI Revolution · 2026-05-02 · communityThis video is a tech news roundup produced and narrated by the YouTube channel AI Revolution. It covers four major AI developments: the accidental leak of Anthropic’s next-tier model Claude Mythos (also codenamed Capybara), Meta FAIR’s brain-response foundation model TRIBE v2, the openJiuwen community’s…
More videos (11)
- The Most Dangerous AI Model Ever: Mythos AI Revolution · 2026-05-02
- Is Claude Mythos “Terrifying”? (According to Experts: No.) Cal Newport · 2026-05-02
- Claude Mythos Preview in 6 Minutes Developers Digest · 2026-05-02
- Claude Mythos is too dangerous for public consumption... Fireship · 2026-05-02
- You Actually Do Need to Understand Mythos Hank Green · 2026-05-02
- Claude Mythos is Actually Scary Low Level · 2026-05-02
- Claude Mythos is Delusional Mo Bitar · 2026-05-02
- Claude Mythos Preview: Everything You Need to Know Nick Saraev · 2026-05-02
- Is Mythos too Dangerous? The PrimeTime · 2026-05-02
- Claude Mythos Explained: Anthropic’s Most Dangerous Model Yet TheAIGRID · 2026-05-02
- Claude Mythos and the end of software Theo - t3․gg · 2026-05-02
All videos with Gemini's descriptions: videos · llms-full.txt
Related posts (1)
- Introducing Project Glasswing, powered by Claude Mythos Preview Anthropic @AnthropicAI · x · 2026-04-07
Launched Anthropic's withheld Mythos-class model for defensive cybersecurity with major tech partners, beginning the Mythos/Fable era.
Related events
- Anthropic releases Claude Fable 5 and Claude Mythos 5 — first generally available Mythos-class model ★★★★★
- Anthropic releases Claude Opus 4.7, admits it trails the unreleased Mythos Preview ★★★
- Claude Code source code leaks via a source-map file in the npm package ★★★
Sources (10)
- officialProject Glasswing (Anthropic)
- officialAssessing Claude Mythos Preview's cybersecurity capabilities
- officialClaude Mythos Preview's cybersecurity capabilities (red.anthropic.com)
- officialClaude Mythos product page
- pressGoogle Cloud: Claude Mythos Preview on Agent Platform
- docsAWS Bedrock model card: Claude Mythos Preview
- discussionCETaS (Turing Institute): What does Mythos mean for cybersecurity?
- discussionWikipedia: Claude Mythos
- videoProject Glasswing video (Anthropic)
- officialAnthropic on X: Introducing Project Glasswing, powered by Claude Mythos Preview
id: 2026-04-07-claude-mythos-preview-project-glasswing · updated 2026-09-29 · open in the interactive timeline